Final answer:
The empirical formula represents the simplest ratio of atoms in a compound. The empirical formulas for a), b), and c) are NaC2H2O2, C2H4, and CO2 respectively. The empirical formula that is NOT listed among the options is CO.
Step-by-step explanation:
The empirical formula is the simplest ratio of the atoms in a compound. To determine the empirical formula, we need the molecular formula and calculate the ratio of the atoms. The empirical formula represents the relative numbers of each type of atom in a compound.
Out of the given options, the empirical formulas for a), b), and c) are NaC2H2O2, C2H4, and CO2 respectively.
Therefore, the answer is d) CO, as it is not an empirical formula.